Ch. 13 Enzymes - Clinical Enzymology Lecture Flashcards
Specific biologic proteins that catalyze biochemical reactions w/o altering the equilibrium point of the rxn or being consumed or changed in composition
Enzymes
Enzymes are frequently found in _____ following cellular injury
Serum
A cavity of an enzyme where substrates bind and undergo a chemical reaction.
Active Site
A water-free cavity, where the substance on which the enzymes acts interacts with particular charged amino acid residues.
Active Site
The substance on which the enzyme acts.
Substrate
A cavity other than the active site that binds regulatory (effector) molecules.
Allosteric Site
Substances acted upon by enzymes
Substrate
Enzymes that have similar enzymatic activity but differ in physical, biochemical and immunologic characteristics
Isoenzymes
Enzymes with the same catalytic function throughout the body but exists in different forms within the same individual
Isoenzymes
Results when an enzyme is subject to posttranslational modifications.
Isoform
Non protein substances added in the enzyme substrate complex to manifest the enzyme activity
Cofactor
Non protein molecule that may be necessary for enzyme activity
Cofactor
Inorganic cofactors
Activators
Organic cofactor
Coenzyme
A coenzyme that is bound tightly to the enzyme
Prosthetic group
Which is/are not an activator: Vitamins Chloride ion Nicotinamide adenine dinucleotide Magnesium ion Nicotinamide adenine dinucleotide phosphate Copper ion
NAD
Vitamins
Nicotinamide adenine dinucleotide phosphate
Which is/are not a coenzyme: Vitamins Chloride ion Nicotinamide adenine dinucleotide Magnesium ion Nicotinamide adenine dinucleotide phosphate Copper ion
Chloride ion
Magnesium ion
Copper ion
The protein portion of the enzyme that is also subject to denaturation, in enzyme losses activity
Apoenzyme
An active substance formed by combination of a co-enzyme and an apoenzyme.
Holoenzyme
Enzymes originally secreted from the organ of production in a structurally inactive form
Proenzyme or Zymogen
Catalyze redox reaction between two substrates (A- + B → A + B-)
Oxidoreductases 1
Catalyze the transfer of a group other than hydrogen (Phosphate, methyl, etc.) between two substrates (A-X + B → A + B-X)
Transferases 2
Catalyze hydrolysis of various bonds
A–B + H2O → A–OH + B–H
Hydrolases 3
Catalyze the removal of groups from substrates without hydrolysis; the product contains double bonds
ATP → cAMP + PPi
Lyases 4
Catalyze the interconversion of geometric, optical or positional isomers
A → B
Isomerases 5
Catalyze the joining of two substrate molecules, coupled with breaking of pyrophosphate bond in ATP or a similar compound
Ab + C → A–C + b
Ligases 6
Which among the given is/are Hydrolases: Phosphatase (ALP, ACP) Glutathione Synthetase (GSH-S) Triphosphate isomerase (TPI) Lipase (LPS) Fructose biphosphate aldolase (ALS) Amylase (AMS) Transferase (ALT, AST, GGT) Dehydrogenase (Lactate Dehydrogenase) Kinase (CK)
Amylase (AMS), Lipase (LPS), Phosphatase (ALP, ACP)
Which among the given is/are Oxidoreductases: Phosphatase (ALP, ACP) Glutathione Synthetase (GSH-S) Triphosphate isomerase (TPI) Lipase (LPS) Fructose biphosphate aldolase (ALS) Amylase (AMS) Transferase (ALT, AST, GGT) Dehydrogenase (Lactate Dehydrogenase) Kinase (CK)
Dehydrogenase (Lactate Dehydrogenase)
Which among the given is/are Transferases: Phosphatase (ALP, ACP) Glutathione Synthetase (GSH-S) Triphosphate isomerase (TPI) Lipase (LPS) Fructose biphosphate aldolase (ALS) Amylase (AMS) ALT AST GGT Dehydrogenase (Lactate Dehydrogenase) Kinase (CK)
ALT, AST, GGT, CK
Which among the given is/are Lyases: Phosphatase (ALP, ACP) Glutathione Synthetase (GSH-S) Triphosphate isomerase (TPI) Lipase (LPS) Fructose biphosphate aldolase (ALS) Amylase (AMS) ALT AST GGT Dehydrogenase (Lactate Dehydrogenase) Kinase (CK)
Fructose biphosphate aldolase (ALS)
Which among the given is/are Isomerases: Phosphatase (ALP, ACP) Glutathione Synthetase (GSH-S) Triphosphate isomerase (TPI) Lipase (LPS) Fructose biphosphate aldolase (ALS) Amylase (AMS) ALT AST GGT Dehydrogenase (Lactate Dehydrogenase) Kinase (CK)
Triphosphate isomerase (TPI)
Which among the given is/are Ligases: Phosphatase (ALP, ACP) Glutathione Synthetase (GSH-S) Triphosphate isomerase (TPI) Lipase (LPS) Fructose biphosphate aldolase (ALS) Amylase (AMS) ALT AST GGT Dehydrogenase (Lactate Dehydrogenase) Kinase (CK)
Glutathione Synthetase (GSH-S)
Which of the following is/are not Transferases: Phosphatase (ALP, ACP) Glutathione Synthetase (GSH-S) Triphosphate isomerase (TPI) Lipase (LPS) Fructose biphosphate aldolase (ALS) Amylase (AMS)
All of the above
Which of the following is/are not Hydrolases: Glutathione Synthetase (GSH-S) Triphosphate isomerase (TPI) Fructose biphosphate aldolase (ALS) ALT GGT Dehydrogenase (Lactate Dehydrogenase) Kinase (CK)
All of the above
Which of the following is/are not Lyases: Glutathione Synthetase (GSH-S) Triphosphate isomerase (TPI) Fructose biphosphate aldolase ALS
Glutathione Synthetase (GSH-S) Triphosphate isomerase (TPI)
The energy required to raise all molecules in 1 mol of a compound at a certain temperature to the transition state t the peak of the energy barrier.
Activation Energy
Catayze physiologic reactions by lowering the activation energy level that the reactants (substrates) must reach for the reaction to occur
Enzymes
The physical binding of a substrate to the active site of an enzyme
Enzyme-substrate complex
Refers to an enzyme combining with only one substrate and catalyzes only the one corresponding reaction.
E.g. CK, LD
Absolute Specificity
Refers to enzymes that combine with all substrates containing a particular chemical group, such as phosphate ester.
E.g. ACP, ALP
Group Specific
Refers to enzymes that are specific to chemical bonds
Bond Specificity
Refers to enzymes that predominantly combine with only one optical isomer of a certain compound.
E.g. LDH, G6PD
Sterioisometric specificity
The following are Group specific enzymes except: CK LDH ALP G6PD
CK
LDH
G6PD
Which of the following enzymes exhibit Absolute Specificity? CK LDH ACP LDH
CK
Enumerate the factors that influence enzymatic reactions
Substrate Concentration Enzyme Concentration pH Temperature Cofactors Inhibitors
Hypothesized that the substrate readily binds to free enzyme at a low substrate concentration.
Michaelis and Menten
It follows that the reaction rate is directly proportional to the substrate concentration.
First-order kinetics
A reaction wherein only a fixed number of substrate (in excess) is converted to product per second; the reaction rate depends only on enzyme concentration
Zero-order kinetics
Changes in _____ may denature an enzyme or influence its ionic state, resulting in structural changes or a change in the charge of an amino acid residue in the active site.
pH
Used to carefully control and maintain the optimal pH in a reaction.
Buffer solutions
Common pH range; most physiologic reactions occur in this range.
7.0 - 8.0
Increasing _____ usually increases the rate of a chemical reaction by increasing the movement of molecules, the rate at which intermolecular collisions occur, and the energy available for the reaction
Temperture
Incubation of enzymes should be accurate within what temperature
(+/-) 0.1 C
Non protein entities that must bind to particular enzymes before a reaction occurs.
Cofactors
The following are some metallic activators except: Ca2+ Fe2+ Zn2+ K+ Br- Mg2+ Mn2+ Cl-
Br-
Cl-
The following are some nonmetallic activators except: Cl- Ca2+ Fe2+ Br- Mg2+ Mn2+ Zn2+ K+
Ca2+ Fe2+ Mg2+ Mn2+ Zn2+ K+
Serve as second substrates for enzymatic reactions
Coenzymes
Increasing _____ concentration will increase the velocity of an enzymatic reaction in a manner synonymous with increasing substrate concentration.
Coenzyme
A particular substance that interferes with enzymatic reactions
Inhibitor
A type of inhibitor that physically binds to the active site of an enzyme and compete with the substrate for the active site.
Competitive inhibitor
In competitive inhibition, the inhibition is reversible when the inhibitor is (greater/less than) the substrate. Explain.
Less than. The inhibition is reversible because the substrate is more likely than the inhibitor to bind to the active site.
Inhibition wherein the inhibitor binds to the ES complex
Uncompetitive inhibition
An inhibitor that binds an enzyme at a place other than the active site and may be reversible in that some naturally present metabolic substances combine reversibly with certain enzymes
Noncompetitive inhibitor
Explain why noncompetitive inhibtion may be irreversible and why increasing substrate concentration will not reverse the inhibition.
Noncompetitve inhibition may be irreversible when the inhibitor destroys part of the enzymes involved in catalytic activity. Increasing substrate concentration will not reverse the inhibition because the inhibitor binds directly to the enzyme.
Km stands for
Michaelis-Menten constant
It is an expression of the relationship between the velocity of an enzymatic reaction and substrate concentration
Km
Indicates the amount of substrate needed for a particular enzymatic reaction
Km
In Competitive inhibition, Km (increased/decreased/was unchanged)
Increased
In Noncompetitive inhibition, Km (increased/decreased/was unchanged)
Unchanged
In Uncompetitive inhibition, Km (increased/decreased/was unchanged)
Decreased
This type of inhibition can be counteracted by adding excess substrate to bind the enzyme.
Competitive inhibition. Reaction will proceed at a slower rate but to the same maximum velocity (Vmax) as an uninhibited reaction.
In this type of inhibition, maximum velocity cannot be achieved.
Noncompetitive inhibition
When substrate concentration is increased, inhibition is also increased in this type of inhibition. Also, maximum velocity equal to that of an uninhibited reaction cannot be achieved.
Uncompetitive inhibition.
A type of inhibition where:
Km increased
Vmax same with uninhibited reaction
Competitive inhibition
A type of inhibition where:
Km is unchanged
Vmax cannot be achieved
Noncompetitive inhibition
A type of inhibition where:
Km is decreased
Vmax equal to that of an uninhibited reaction cannot be achieved
Uncompetitive inhibition
What are the functions of Enzymes?
Hydration of Carbon Dioxide (respiration) Nerve Induction Muscle Contraction Nutrient Degradation (Digestion) Growth and Reproduction Energy Storage and Use